body{
}

.tt div{
    margin:auto;
    width:200px;
    height: 40px;
    border:8px solid gold;
}
.test{
}
.border-box{
    box-sizing: border-box;
    -webkit-box-sizing: border-box;
}
.tt2 div{
    width:200px;
    height: 40px;
    border:8px solid #ff0000;
}
.tt2 .box{
    display: -webkit-flex;
    -webkit-box-orient: vertical;
    -webkit-box-direction: reverse;
    -webkit-box-lines: multiple;
    margin-bottom: 100px;
}
.tt2 .box .box-flex{
    width: 100px;
    border:8px solid green;
    -webkit-box-flex:1;
}
.tt2 .box .box-flex2{
    width: 40px;
    border:8px solid green;
    -webkit-box-flex:1;
}

.layout-demo{
    width:960px;
    border:4px solid #ff0000;
}

#header{
    background: orange;
    width: 100%;
}
#content{
    clear: both;
}

#left{
    width: 220px;
    margin-right: 20px;
    background: green;
    float: left;
}

#main-content{
    width: 720px;
    background: gray;
    float: left;
}
#footer{
    background: gold;
    width: 100%;
}

.inner-padding {
    padding: 10px;
}

.border {
    border: 10px solid yellow;
}

.box-sizing {
    -moz-box-sizing: border-box;
    -webkit-box-sizing: border-box;
    -o-box-sizing: border-box;
    -ms-box-sizing: border-box;
    box-sizing: border-box;
}